1. Field of the Invention
The present invention relates to a mounting aid for the alignment of a first graduation support of a position measuring system. The present invention further relates to a scale with a mounting aid for the alignment of the scale relative to a scanning unit of a position measuring system. The present invention also relates to position measuring system with a scale and a scanning unit.
2. Discussion of Related Art
A position measuring system contains two graduation supports, which are movable with respect to each other for a position-dependent modulation of a physical value. One of these graduation supports is the scale with a graduation, which can be designed to be incrementally or absolutely coded. In the course of the position measurement, this graduation of the scale is scanned by a graduation of a further graduation support. This graduation is a scanning graduation of a scanning plate or the arrangement of detector elements.
When being installed on parts of machinery, these two graduation supports must be aligned with respect to each other. An essential parameter in this case is the so-called scanning distance, i.e. the distance between the graduation of the scale and the graduation of the scanning unit.
Mounting aids for setting the scanning distance are already known. In accordance with EP 0 177 711 B1, the scanning unit has a slit, through which a foil of defined thickness can be introduced between the measuring graduation and the scanning graduation from the outside. The thickness of the foil corresponds to the required scanning distance. Adjusting the scanning distance is performed by moving the scanning unit until it clamps the foil. The scanning unit is screwed onto a part of a machine in the clamped state and thereafter the foil is removed by pulling it out of the slit. It is stated that the foil is included with the measuring device and possibly performs a further function as the warranty document.
A self-adhesive foil, whose thickness corresponds to the desired scanning distance, is provided for setting the scanning distance in DE 102 29 888 A1. The scale is protected against damage by the self-adhesive foil during the alignment and attachment. The disadvantage of a self-adhesive foil is the possible effect of remaining residue from the adhesive layer on the measuring graduation. Moreover, handling of the self-adhesive foil is impractical, since it can only be removed by pulling it off, for which a sufficient free space must be available after the installation of the scanning unit and the scale.